Apparatus and method for separating and replacing a cap from a shank of a tip of a welding electrode

Method of separating and replacing first and second caps from first and second shanks of first and second tips of welding electrodes, said tips facing each other in a closable clamp arrangement and being held by opposite fingers pivotally mounted on an arm of a welding robot, said caps and said shanks forming first and second peripheral hollow joints that are defined by recessed end surfaces of the shanks and back surfaces of the caps, the method comprising the steps of:

• a) inserting the first tip of the first welding electrode, by means of the robot welder, in a first recessed portion of a first guide frame, said first recessed portion extending in a direction perpendicular to said first tip and having two first facing side walls provided with first guiding ribs and a first end wall;
• b) guiding the first tip of the first electrode by means of the first guiding ribs of the first side walls that are inserted in the first peripheral hollow joint until the first tip of the first welding electrode is abutted against the first end wall in a first engaged position;
• c) detecting that the first tip of the first welding electrode is in the engaged position;
• d) moving a first cap withdrawing tool in a closed position, said first tool being mounted on the first guide frame along a first crosswise direction that is perpendicular with respect to both the first tip and the first recessed portion, said first tool having two facing wall sections each having a wedge being inserted in the first peripheral hollow joint and forced against the back surface of the first cap, thereby removing the first cap from the first shank;
• e) moving said first cap withdrawing tool in an open position along the crosswise direction and simultaneously actuating an indexing mechanism that moves a first new cap mounted on a first holder of a cap supply drum in a home position;
• f) positioning the first and second tips by means of the robot welder in the home position where the first tip is in alignment with the first new cap;
• g) closing the first tip against the second tip to insert the first new cap into the first shank of the first tip;
• h) inserting the second tip of the second welding electrode, by means of the robot welder, in a second recessed portion of a second guide frame, said second recessed portion extending in a direction perpendicular to said second tip and having two second facing side walls provided with second guiding ribs and a second end wall, said second guide frame being upside down with respect to the first guide frame;
• i) guiding the second tip of the electrode by means of the second guiding ribs of the second side walls that are inserted in the second peripheral hollow joint until the second tip of the welding electrode is abutted against the second end wall in a second engaged position;
• j) detecting that the second tip of the welding electrode is in the engaged position;
• k) moving a second cap withdrawing tool in a closed position, said second tool being mounted on the second guide frame along a second crosswise direction that is perpendicular with respect to both the second tip and the second recessed portion, said second tool having two facing wall sections each having a wedge being inserted in the second peripheral hollow joint and forced against the back surface of the second cap, thereby removing the second cap from the second shank;
• l) moving said second cap withdrawing tool in an open position along the crosswise direction and simultaneously actuating the indexing mechanism that moves a second new cap mounted on a second holder of the cap supply drum in the home position;
• m) positioning the first and second tips by means of the robot welder in the home position where the second tip is in alignment with the second new cap;
• and
• n) closing the second tip against the first tip to insert the second new cap into the second shank of the second tip.

Apparatus for separating a cap from a shank of a tip of a welding electrode, said cap and said shank forming a peripheral hollow joint that is defined by a recessed end surface of the shank and a back surface of the cap, the apparatus comprising:

• a guide frame having a recessed portion sized for receiving the tip of the welding electrode, said recessed portion extending in a direction perpendicular to said tip and having two facing side walls and an end wall, the side walls having guiding ribs that are inserted in the peripheral hollow joint for guiding the tip of the welding electrode into the recessed portion until the tip of the welding electrode is abutted against the end wall in an engaged position;
• a cap withdrawing tool movably mounted on the guide frame, said cap withdrawing tool being movable along a crosswise direction that is perpendicular with respect to both the tip and the recessed portion when the tip of the welding electrode is in the engaged position, said tool having two facing wall sections each having a wedge provided with a knife edge that is inserted in the peripheral hollow joint when the tool is moved toward the tip of the electrode that is in the engaged position, said knife edge of the wedge being forced into the back surface of the cap for removing the cap from the shank when the tool is moved toward the tip of the electrode;
• and
• a driving mechanism coupled to the cap withdrawing tool for moving the cap withdrawing tool toward and away from the tip of the welding electrode along the crosswise direction between an open position where the tip of the electrode is inserted into and removed from the recessed portion of the guide frame and a closed position where the wedge removes the cap from the shank.